1. Technical Field
The present invention relates to an imaging display system.
2. Description of the Related Art
A typical imaging device, such as a digital camera, frequently includes a rolling shutter image sensor serving as a complementary metal oxide semiconductor (CMOS) image sensor having a line sequential scanning system. Such a rolling shutter image sensor causes image distortion (hereinafter, also referred to as moving body distortion) in capturing a moving body moving within the angle of view of the image sensor because there is a time lag in exposure start time of each line. Especially in an imaging display system that synchronizes a scanning direction of an image sensor with scanning of a display device to perform display, an image of the moving body displayed on the display device is obliquely distorted if the scanning direction of the image sensor does not coincide with the moving direction of the moving body. To install a camera on a body of a car and implement a digital mirror function that displays an image outside the car on an on-board display device to assist driving of a driver, for example, the driver may possibly erroneously recognize the distance to a car moving parallel thereto or a car moving on the opposite lane.
By contrast, a global shutter image sensor having a batch exposure system, such as a charge coupled device (CCD) image sensor, causes no moving body distortion occurring in the rolling shutter image sensor. Even in a case where a CMOS image sensor having a line sequential scanning system is used, the use of a mechanical shutter enables the CMOS image sensor to serve as a global shutter image sensor, such as a CCD image sensor. This mechanism, however, complicates the control, increases the number of parts, and causes the device to be larger because of the increase in the number of parts. In addition, this mechanism fails to cause the display frame rate in display of the image on the display device to be equal to or higher than a repetition frequency between a shutter close period and a shutter open period (batch exposure time). Japanese Patent Application Laid-open Publication No. 2008-157880 (JP-A-2008-157880), for example, describes an on-board camera device including a CMOS image sensor that implements a global shutter function without using any mechanical shutter.
The CMOS image sensor described in JP-A-2008-157880, however, requires a circuit that implements the global shutter function in the image sensor, thereby complicating circuits included in the image sensor. This configuration causes the area of a photodiode to be smaller and reduces the aperture ratio. As a result, the CMOS image sensor has a lower sensitivity and a narrower dynamic range than a CMOS image sensor having no global shutter function.
For the foregoing reasons, there is a need for an imaging display system that can eliminate or reduce erroneous recognition of a visible distance caused by moving body distortion in an image displayed on a display device without complicating a circuit in an image sensor.